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Winter Tire Safety Tips

Published Mar 25th 2008, 10:21pm by

Snowtire Winter brings many challenges for your car each year, but perhaps the most nerve-wracking is the hazardous driving conditions you'll have to face. Even though the groundhog has already seen its shadow, it's not too late to consider switching your all-season tires to winter ones for increased safety and peace of mind.

Rubber compounds in tires are made to perform in specific temperatures: summer tires are very firm, winter tires are more flexible, and all-seasons are somewhere in between. The main reason winter tires are not just called "snow tires" anymore is because they are designed to offer the best traction possible on snow and ice...and on dry and wet conditions.

"Winter tires perform much better than an all-season tires in colder temperatures," says Tony Talbert, light truck and winter product manager for Continental Tire North America. "If you live in an area where the average winter temperature is below 45 degrees Fahrenheit, the tread compounding has a dramatic effect on your traction capability. If you live in an area where you have an extended period of time with an average temperature below that, we recommend a winter tire."

"It's not just the amount of snow because in low temperatures, winter tires perform better, even on dry pavement, than all season tires," says Bill VandeWater, director of consumer products in sales engineering for Bridgestone/Firestone North American Tire. "You might be in an area of the country that doesn't get snow, but if it gets cold, it's still appropriate to look at winter tires."

Talbert says depending on the brand and type of tire, winter tires remain flexible in extreme temperatures, down to as low as -40*F.

Muddytire What to Look For
As with other tires, there are many choices when it comes to selecting winter tires. Some things to look for that differentiate them from summer or all-seasons are added sipes (small cuts or slots in the tread) and irregularly shaped tread blocks for enhanced grip. The irregular shape provides more "biting edges" that provide added grip on poor road conditions.

"The tread pattern is much more broken up," VandeWater says. "What you want to have in order to get good grip, in the snow especially, is a lot of cross slots and notches in the tire in order to provide edges that grip into the snow. In addition, the tread elements are usually smaller so we can fit more of them around the circumference."

A tire that meets the performance criteria for a winter tire will have a symbol on the sidewall depicting a mountain peak with a snowflake in front of it. This icon, called both an "alpine" or "mountain snowflake" symbol, is a good indication of a quality tire, VandeWater says.

This icon replaced a former symbol, the letters "M+S" (for "mud and snow"), which meant the tire had design characteristics that made it appear to be a winter tire, but no performance testing attached, he says. M+S tires are now generally all-season products.

Winter tires should be put on your vehicle once the average temperature consistently drops below 45*F, and taken off once temperatures increase above that range in the spring, Talbert says.

Even on vehicles that are front- or rear-wheel drive, all four tires should be swapped for winter tires, not just two. This is because cornering is dependent on all four tires having equal traction.

"You'll gain a little bit of acceleration traction (with only two winter tires), but the first time you go into a corner where you're needing lateral traction, your car will become completely unbalanced and uncontrollable," Talbert says.

"It's a recommendation based on safety - we see a significant performance difference in low temperatures," he says. "Regardless of what brand the tire is, there's a difference in that compound."

Rain_driving Worth the Expense
It's that difference that primarily outweighs the cost of another set of tires and the hassle of switching them out twice a year, because it all boils down to safety.

Talbert cited an example that at a speed of just under 30mph, a car with winter tires will stop on a snowy surface about 26 feet sooner than a car clad with all-season tires.

"If you get into a panic, with a car stopped in front of you or a child who runs out in front of you, having winter tires can make a difference between hitting this child or not," he says. "There is a huge amount of safety to be gained simply because a winter tire is designed for winter conditions."

From a cost perspective, Talbert says purchasing a winter set is a one-time only added expense, with tire dealers often storing the off-season set for little or no cost, and charging a minimal fee to mount and dismount twice a year.

"The mileage you're putting on your winter tires is mileage you're not putting on your other set, so it's making that set last longer," VandeWater says. "Also, if you spend $300 or $400 for winter tires but they keep you out of an accident, one accident for the typical insurance deductible would cost more than that."

Even vehicles with ABS, four-wheel drive or traction control may be giving you a false sense of security on wintry roads, since those systems can only work as well as the amount of grip from tires allows.

"If that traction is poor from not having the appropriate tire, then you're not gaining nearly the amount of benefit (from those systems) as you'd have if you had good traction to begin with," Talbert says. "Regardless of the system you may have, the only interface between your vehicle and the road is that contact patch of the tire itself, and you have to maximize the capability of that contact patch."

"Those are all very good systems, but they don't touch the ground," VandeWater agrees. "They work through the tires and the better the tires you have on, the better those systems will work."

Winter Tire Maintenance
Like all tires, winter tires must get regular air pressure checks to ensure they're offering the best performance - traction and treadlife - possible. Tires tend to lose about 1 psi each month on their own, but coupled with drastic temperature declines, air pressure inside tires may drop significantly.

"Pressure inside a tire is dependent upon ambient temperature," VandeWater Says. "If the temperature goes down, the pressure in that tire will go down (about 1 psi for every 10 degrees). You need to check the pressure in your tires every month to make sure that you compensate for those potential temperature drops, because it's the air in a tire that carries the load of the vehicle, not the tire itself."


By Denise Koeth
Managing Editor, www.tirereview.com

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